Electrical signaling-circuit



(No Model-) h T. D. .LOCKWOODC ELECTRICAL SIGNALING CIRCUIT.

Patented June 6, 1882.

i l i'ness e5.- fiwwza M NITjED STATES PATENT OFFICE.

THOMAS D. LOCKWOOD, OF MALDEN, MASSACHUSETTS.

IELECTRICALSIGNALING-CIRCUIT.

SPECIFICATION forming part of Letters Patent N0. 258,934, dated June 6, 1882.

' Application filed April 12, 18 82. (No model.)

To all whom it may concern Be it known that I, THoMAs D. LOCKWOOD, of M alden, in the county of Middlesex and State of Massachusetts, have invented certain Improvements in Electrical Signaling-Circuits, of which the following is a specification.

My invention relates to improvements in telephonic central-office apparatus, and especially to that class known as annunciators.

It is now universally known that in the central office of a system of telephonic intercommunication it is necessary that some indicating apparatus be provided, whereby the subscribers may attract the attention of the central-office operator for the purpose of making known to him his desires. The device most frequently adopted is an annunciator which shows a visual signal, and which consists, broadly speaking, of an electro-magnet in the main-line circuit, which controls an armature and signaling device. Wheneveran electrical impulse is transmitted through the magnet-coils from the subscribers station the armature is attracted, and the signal correspondingly operated, usually by the dropping of a specially colored or configured shield. It is in many telephone-exchanges customary upon the receipt of such a signalfrom the subscribers station to respond to the same before replying orally by sending a short seriesof electric pulsations to line, which, traversing the circuit, produce an answering ring upon the bell of the subscriber, notifying him thereby that his call is receiving the attention of the operator. This responsive ring, though in many respects convenient, takes time, and

since time and its economy are important c011- siderations in the operation of a telephone-exchange, what would otherwise be advantageous becomes disadvantageous, simply on account of the time consumed in its accomplishment.

To achieve the transmission of a returnring independent of any manual operation on the part of the operator, and consequently witha great saving of time, is the object of my invention.

My invention consists in constructing the support upon which the annunciator-drops fall of metal, and placing the same in electrical connection with a wire leading from one terminal of a battery furnished with a polechanger, or of a magneto or dynamo electric machine or other source of current electricity, preferablyin a state of continuous alternation. It further consists in the combination, with the drop support or anvil, arranged as above, of an annunciator-drop; adapted, when operated, to sever the line-circuit from its ground terminal, and to transfer the said line to a new terminal through a sourceof current-electricity.

In the drawings by which my invention is illustrated, and which form apart of this specification, Figure 1 is a diagram representing my apparatus in its normal or quiescent condition. Fig. 2 is the same apparatus in operation, the'drop having been caused to fall. Fig. 3 is a modification of the circuit arrangement in which the main circuit is not broken bythefallot the nnnuneiator-drop, but a derived circuit is established, including the electrical generator. Fig. 4. is a diagram, repre senting a number of lines combined with a dynamo-electric machine, in accordance with the terms of my invention.

In the drawings, D is the call-box at a subscribers station,'and is connected by the1incwire L and ofiice-wire 5 with its annunciator A at the central station, and by the groundwire 6 with the earth. ()ne terminal of the annunciator-coils It being connected with the line by the office-wire 5, the other terminal is connected by the wire 3 to the drop-lever a, and thence, by means of the fiat spring I), attached to the block 0, and the wire 4 to the ground G. It will be at once seen that the circuit is thus completed, and may be traced as follows: groundG, wire 4, block 0, spring I),

metallic drop-lever a, wire 3, helices h, wire 5,

line-wire L, subscribers bell D, and wire 6to ground G at substation.

Just below and in front of the annunciatordrop a is a metallic support or anvil, 2, permanently connected electrically by the wire 1 with an electrical generator, 0, which I have shown as a magneto-electric machine, driven by power derived from the pulley B, but which may, if desired, be a battery, properly furnished with a pole-changing device, or any suitable source of electricity. If the subscriber operates his bell-box D at the substation, an electrical current is produced, which, besides ringing his own bell, traverses the line-wire L and vitalizes the helices h, causing the armature d to be attracted, and releasing the drop lever a, permitting it to fall on the plate 2.

In Fig.4 I have shown in diagram the relative arrangement of the annnnciators A, belonging to the several circuit-wires L of the exchange, and of the anvil 2, connected by wire 1 with the dynamo-machine E.

Fig. 2 shows the same arrangement of apparatus exemplified in Fig. 1 but illustrates the operation of the device. In it the droplever is shown as having fallen. Thus the contact between thedrop-lever a and flat spring b is broken, and a new contact between the drop-lever and the anvil 2 is formed. The course of the line-circuit is thus transferred from the ground to the generator E, and the circuitof the said generator being thus closed, a succession of currents originated therein are transferred through anvil 2 and drop-lever a over the line L to the ground G at the substation, passing en route through the bell D and causing it to ring and give the subscriber an audible response to his call,wherebyhe is notified that his signal has been received and will be attended to.

It has been found in practice that this operation may be satisfactorily accomplished without necessarily removing the ground-circuit before connecting the generator,and I have in some cases found it preferable to organize the connections on the plan delineated in Fig. 3. When this is done I cause the line-circuitL to bifurcate at the point as. One of the diverging branches is then led by the wire 5 through the helices h and wire 3 to ground, while the other is formed by the wire 7 to the metal framef of the annunciator, which is always in metallic contact with the drop-lever a. The wire 7 is permanently attached to the frame (1, and thus when the drop a falls and makes contact with the anvil 2 a new circuit is established in addition to the old, and in practice it is found that, although a certain amount of the elec tricity generated by the machine E diverges at the pointx and flows backward through wire 5and the helices h to earth,a sufficient amount flows to line and to the distant ground to give a satisfactory ring on the substation hell.

I am aware that heretofore an apparatus has been arranged for the purpose of notifying a subscriber that his call has reached the central station by causing the line-circuit to open and the subscribers bell to cease ringing after the lapse of a definite period of time. I do not, therefore, claim such an arrangement, the essence of my invention being the organization of circuits and apparatus by which the centraloffice annunciatordrop, when caused to fall by the action of the distant subscriber, breaks its own line-circuit, or establishes an auxiliary circuit connected with the line-circuit, and further places the line-circuit in such connection with a constant source of electricity that a succession of electrical pulsations are automatically transmitted over it from the central station to the substation. notifying the subscriber by ringing his hell that his call has been received and will be attended to.

I claim- 1. A mainline, an annunciator, and a branch circuit to earth direct, combined with a magneto-electric machine or other generator of electricity in a normally-open branch circuit, and an electric switch automatically operated by the annunciator and adapted to change the circuit of the main line from the earth branch circuit to the normally-open generator branch circuit.

2. The combination, substantially as hereinbefore described, ot' a series of main-line circuits, each provided with an annunciator, and branch circuit to earth direct, with a normallyopen branch circuit, including a magneto-electric generator or other source of electricity common to the series of main lines, and means, substantially as indicated,whereby one or more of the main lines may be connected to the said generator for the purpose of transmitting a return-signal over the main line or lines so connected.

3. The electric generator, the anvil forming a support for the annunciator-drops, anda conducting-wire connecting one with the other, combined with the electro-mechanical switch or circuit-changer, and a main line annunciator, as described.

In testimony whereofI have signed my name to this specification, in the presence of two subscribing witnesses, this 10th day ofApril,1882.

THOS. D. LOGKWOOD.

\Vitnesses J. H. CHEEVER, Geo. WILLIs PIERCE.

ICC 

